Generally, a passenger car body for a rail vehicle is supported by two bogies respectively situated toward the two ends of the body. Each bogie generally comprises two axles, and each bogie is linked on the one hand to each axle by a primary suspension device with helical springs for example, and on the other hand to the body of the car by two secondary air suspension devices which are each associated, for reasons of safety, to an emergency device suitable for compensating any leak of air in the associated secondary suspension and which could possibly provoke a derailing of the rail vehicle running at high speed.
The role of these secondary air suspensions is essentially to improve the comfort of the passengers, and they therefore have to offer a very wide flexibility. Physically, a secondary air suspension consists of a flexible and air-tight membrane, which can take the form of a tire linked to an auxiliary air tank to increase the volume of air stored in the membrane. The document FR-A1-2 896 220 can, for example, be cited for the description of such a secondary air suspension.
As is known, these secondary air suspension membranes are reinforced by sheets of woven textile fabrics (inlaid textiles) which are embedded in rubber, as for example described in the document EP-A1-1 918 609 which mentions such textile/rubber composite fabrics and as illustrated in FIG. 8 appended to the present description which shows a phase of forming, on a mandrel a, of a woven sheet b of such a known membrane. As can be seen in this FIG. 8 which also shows two rods c provided to reinforce two attachment areas of the membrane and between which the sheet b is intended to extend, the latter comprises warp threads b1 which extend substantially in the axial direction YY of the mandrel a and which are linked together by weft threads b2 which extend substantially in the circumferential direction of the mandrel a. It can also be seen in this FIG. 8 that the duly formed woven sheet b necessarily has an overall axial area of overlap b3 (known as “duplicature” to those skilled in the art) defining two thicknesses of this sheet b at its connection around the mandrel a.
A major drawback with these known membranes with woven fabric sheets lies in their relatively low mechanical strength in operation. In particular, the doubling of the density of threads b1, b2 in this area b3 constitutes an obstacle to the uniform expansion of the membrane when inflating the membrane preform before vulcanization, which generates a line of mechanical weakness of the membrane in use.